Zeolites or molecular sieves used for catalysts are often formed into shaped body by binding with binder materials. Commonly used binder materials include alumina, silica, silica-alumina, clay, or combinations of these materials. When using shaped catalyst it is important that the catalyst has sufficient physical integrity during its use in commercial reactors. Without sufficient physical strength, the catalyst can be damaged or degrade, creating fines and debris that can have negative consequences on the reaction and the reactor equipment. Several measurements are performed to determine physical integrity of a shaped catalyst. Such measurements include attrition resistance, bulk crush strength, particle crush strength, etc.
Certain binder materials may impart better physical or mechanical properties to the shaped zeolite catalyst than others. The particular binder material used, however, may also affect the reaction or reactions, making the use of certain binders that provide better strength unsuitable in certain applications. For example, certain reactions are affected by acidity. Although alumina, which is a commonly used as a binder material, has weak acidity, the weak acidity can still affect certain reactions. Silica has low or no acidity making it useful as a binder in those reactions that are affected by acidity. Catalyst bound with silica, however, may have lower physical strength than other binder materials.
Accordingly a need exists for improving the mechanical properties of silica bound zeolite catalysts.